Vasopressin is released from the posterior pituitary either in response to increased plasma osmolarity detected by brain osmoreceptors or decreased blood volume and blood pressure sensed by low-pressure volume receptors and arterial baroreceptors. The hormone exerts its action through two well defined receptor subtypes: vascular V.sub.1 and renal epithelial V.sub.2 receptors. Vasopressin-induced antidiuresis, mediated by renal epithelial V.sub.2 receptors, helps to maintain normal plasma osmolarity, blood volume and blood pressure.
Vasopressin is involved in some cases of congestive heart failure where peripheral resistance is increased. V.sub.1 antagonists may decrease systemic vascular resistance, increase cardiac output and prevent vasopressin induced coronary vasoconstriction. Thus, in conditions with vasopressin induce increases in total peripheral resistance and altered local blood flow, V.sub.1 antagonists may be therapeutic agents. V.sub.1 antagonists may decrease blood pressure, induced hypotensive effects and thus be therapeutically useful in treatment of some types of hypertension.
The blockage of V.sub.2 receptors is useful in treating diseases characterized by excess renal reabsorption of free water. Antidiuresis is regulated by the hypothalamic release of vasopressin (antidiuretic hormone) which binds to specific receptors on renal collecting tubule cells. This binding stimulates adenylyl cyclase and promotes the cAMP-mediated incorporation of water pores into the luminal surface of these cells. V.sub.2 antagonists may correct the fluid retention in congestive heart failure, liver cirrhosis, nephritic syndrome, central nervous system injuries, lung disease and hyponatremia.
Elevated vasopressin levels occur in congestive heart failure which is more common in older patients with chronic heart failure. In patients with hyponatremic congestive heart failure and elevated vasopressin levels, a V.sub.2 antagonist may be beneficial in promoting free water excretion by antagonizing the action of antidiuretic hormone, On the basis of biochemical and pharmacological effects of the hormone, antagonists of vasopressin are expected to be therapeutically useful in the treatment and/or prevention of hypertension, cardiac insufficiency, coronary vasospasm, cardiac ischemia, renal vasospasm, liver cirrhosis, congestive heart failure, nephritic syndrome, brain edema, cerebral ischemia, cerebral hemorrhage-stroke, thrombosis-bleeding and abnormal states of water retention.
The following prior art references describe peptide vasopressin antagonists: M. Manning et al., J. Med. Chem., 35, 382 (1992); M. Manning et al., J. Med. Chem., 35, 3895 (1992); H. Gavras and B. Lammek, U.S. Pat. No. 5,070,187 (1991); M. Manning and W. H. Sawyer, U.S. Pat. No. 5,055,448 (1991) F. E. Ali, U.S. Pat. No. 4,766,108 (1988); R. R. Ruffolo et al., Drug News and Perspective, 4 (4), 217, (May) (1991). P. D. Williams et al., have reported on potent hexapeptide oxytocin antagonists [J. Med. Chem., 35, 3905 (1992)] which also exhibit weak vasopressin antagonist activity in binding to V.sub.1 and V.sub.2 receptors. Peptide vasopressin antagonists suffer from a lack of oral activity and many of these peptides are not selective antagonists since they also exhibit partial agonist activity.
Non-peptide vasopressin antagonists have recently been disclosed, Y. Yamamura et al., Science, 252, 579 (1991); Y. Yamamura et al., Br. J. Pharmacol, 105, 787 (1992); Ogawa et al., (Otsuka Pharm Co., LTD.) EP 0514667-A1; EPO 382185-A2; WO9105549 and U.S. Pat. No. 5,258,510; WO 9404525 Yamanouchi Pharm. Co. Ltd., WO 9420473; WO 9412476; WO 9414796; Fujisawa Co. Ltd., EP 620216-A1 Ogawa et al, (Otsuka Pharm. Co.) EP 470514A disclose carbostyril derivatives and pharmaceutical compositions containing the same. Non-peptide oxytocin and vasopressin antagonist have been disclosed by Merck and Co.; M. G. Bock and P. D. Williams, EP 0533242A; M. G. Bock et al., EP 0533244A; J. M. Erb, D. F. Verber, P. D. Williams, EP 0533240A; K. Gilbert et al., EP 0533243A.
Premature birth can cause infant health problems and mortality and a key mediator in the mechanism of labor is the peptide hormone oxytocin. On the basis of the pharmacological action of oxytocin, antagonists of this hormone are useful in the prevention of preterm labor, B. E. Evans et al., J. Med. Chem. 35, 3919 (1992), J. Med. Chem., 36, 3993 (1993) and references therein. The compounds of this invention are antagonists of the peptide hormone oxytocin and are useful in the control of premature birth.
The present invention relates to novel tricyclic derivatives which exhibit antagonist activity at V.sub.1 and/or V.sub.2 receptors and exhibit in vivo vasopressin antagonist activity. The compounds also exhibit antagonist activity at oxytocin receptors.